Objectives: Synchrotron radiation (SR)-based X-ray phase-contrast tomography (XPCT) has proven innovative modality for analysing 3D morphology and is useful for understanding the pathophysiology of various cardiovascular disease. To elucidate pathogenesis of acute type-A aortic dissection (AADA), we evaluated fresh aortic wall samples of AADA with SR-based XPCT.
Methods: Fresh human aortic samples of the ascending aorta (Group-F: n=7) were obtained during emergent aortic repair for AADA, stored in cold saline (4 degree Celsius), and applied XPCT within 24 hours. Formalin-fixed normal aorta (Group-N: n=10), obtained from autopsy, were also investigated. Effective resolution of XPCT in Japan Synchrotron Radiation Research Institute / SPring-8 is 11.7 μm. Dynamic measurement, in which changes in imaging of fresh aortic wall under various tensile force could be visualized, was applied to simulate physiological condition, in which aortic wall is stretched in a horizontal direction according to blood pressure. Pathological analysis was performed, subsequently.
Results: Age of patients was 57.5+9.5 years old in Group-F and 57.5±9.5 in Group-N. In Group-N, density of the tunica media was not different between intimal side (1.083±0.002 g/cm3) and adventitial side (1.085±0.003 g/cm3), and average of medial density was 1.095±0.003g/cm3. On contrast, in Group-F, density of the tunica media was significantly different between intimal and adventitial side (1.145+0.002 vs 1.128+0.003, respectively; p<0.005), and this difference was enhanced according to stretch of the aortic wall. Differences in density within tunica media were well correlated with distribution of elastic fibers and existence of cystic medial necrosis in pathological analysis.
ConclusionS: X-ray phase-contrast tomography was a strong modality to understand aortic structures and pathogenesis of acute type A aortic dissection. Degeneration of tunica media in acute type-A aortic dissection was clearly demonstrated with X-ray phase-contrast tomography.